Have you or a person in your family ever experienced a mini-stroke?

I think my mother had one last Thanksgiving because she suffered loss of motor control along with slurred speech. After a month everything returned to normal. Then while we sat in the car talking she screamed out and stated that she thought she was going to die. She could not explain to me the symptoms and why she said that. A week later her language was confusing and she kept using the wrong words to express herself. I had to keep trying to figure out what she meant. For ex. paper was the remote control, meat, gravy and stuffing were veggies or fruit. She can't remember how to work her DVD. She is very frustrated. She had recently gone to a neurologist for the first episode and all tests (i.e., EEG, MRI, blood workup) were negative except for some old TIAs. He was no help. It could be complex migraine that is bringing the TIA attacks as she has a history of migraines. Don't know what to do.

She is 80 years old with high blood pressure, high cholesterol and is a renal patient.

The first one you describe sounds like TIA: transient ischemic attack. You write everything returned to normal.
The second episode sounds like there was some residual damage; I would call that a stroke, not "transient", therefore I would disagree with the doctor on that. She has memory loss and loss of functional abilities, though it seems minimal - even so, it's not minimal to her if she is frustrated !

At 80 she should not have problem with migraines; they usually decrease or go away after age 50 or 60. It's more likely that she has clotting problem or occlusion which caused the TIA and stroke.
CT or MRI scan should show an area of stroke damage, tho in her case it might be too small to see.
I would get a second opinion in neurology if he has not put her on anti-clotting meds such as plavix or aspirin.

She has all the risk factors. I hope she is on a regular treatment. After the current episode, she should get it if she is not already taking a regular medication.
Neurologist should have advised some medicines.
There are certain age related changes, but treatment should help to some extent.
Good luck with your mom!